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An innovative orbit determination method which makes use of gravity gradientsfor Low-Earth-Orbiting satellites is proposed. The measurement principle ofgravity gradiometry is briefly reviewed and the sources of measurement errorare analyzed. An adaptive hybrid least squares batch filter based onlinearization of the orbital equation and unscented transformation of themeasurement equation is developed to estimate the orbital states and themeasurement biases. The algorithm is tested with the actual flight data fromthe European Space Agency Gravity field and steady-state Ocean CirculationExplorer. The orbit determination results are compared with the GPS-derivedorbits. The radial and cross-track position errors are on the order of tens ofmeters, whereas the along-track position error is over one order of magnitudelarger. The gravity gradient based orbit determination method is promising forpotential use in GPS-denied spacecraft navigation.

Low-Earth Orbit Determination from Gravity Gradient Measurements